Multipersistence display arrangement

ABSTRACT

A multipersistence display device is described which comprises a cathode-ray tube whose faceplate is coated with a layer of an ultraviolet-emitting phosphor. Provided on the ultraviolet phosphor layer is a layer of a phosphor-emitting visible light. The electron beam accelerating voltage of the cathode-ray tube is selectively controlled; a lower voltage causing the electron beam to excite the visible phosphor layer, and higher voltage causing the electron beam to excite the ultraviolet phosphor layer. An image-storage panel is included for storing the ultraviolet image which is produced when the ultraviolet phosphor layer is excited. An optical image system is provided for projecting images appearing on the screen of the cathode-ray tube onto the imagestorage panel. Thus, when the cathode-ray tube is operated at the lower voltage to excite the visible phosphor, dynamic information can be displayed on the image-storage panel and, when the cathode-ray tube is operated at the higher voltage to excite the ultraviolet phosphor, static information can be stored in the image-storage panel and displayed by the action of an electroluminescent material thereby.

United States Patent Euval S. Barrekette New York, N.Y.;

Herbert B. Baskin, Pinole, Califl; Beniamin Kazan, Briarcliff Manor, N.Y.

[72] Inventors [21] Appl. No. 882,071

[22] Filed Dec. 4, 1969 [45] Patented Jan. 11, 1972 [7 3] Assignee International Business Machines Corporation Armonk, N.Y.

[54] MULTIPERSISTENCE DISPLAY ARRANGEMENT 6 Claims, 2 Drawing Figs.

[52] US. Cl 178/7-85,

. 7.8, l78[ l )lG.3l [5 1] Int. Cl H04n 5/74 [50] Field of Search 178/68,

7.8, 5.4 PE, 7.85, DIG. '31

[56] References Cited 4 UNITED STATES PATENTS 3,330,990 7/1967 Guillette l78/5.4 PE OTHER REFERENCES Proceedings of the IEEE, Nov. 1968, Vol. 56, No. 11 pp. 2057- 2059, by Kazan & Foote A New Type of Field Effect Image Storage Panel with a Photoconductive Charging Layer SWITCH LOGIC CONTROL 46 Proceedings of the IEEE, March 1968, Vol. 56, No. 3 pp. 285- 295, by Kazan & Winslow, Image-Storage Panels Based on Field-Effect Control of Conductivity Primary Examiner- Robert L. Richardson Assistant Examiner- Richard K. Eckert, .Ir. Attorneys-Hamlin and .lancin and Isidore Match ABSTRACT: A multipersistence display device is described which comprises a cathode-ray tube whose faceplate is coated and higher voltage causing the electron beam to excite the ultraviolet phosphor layer. An image-storage panel is included for storing the ultraviolet image which is produced when the ultraviolet phosphor layer is excited. An optical image system is provided for projecting images appearing on the screen of the cathode-ray tube onto the image-storage panel. Thus, when the cathode-ray tube is operated at the lower voltage to excite the visible phosphor, dynamic information can be displayed on the image-storage panel and, when the cathode-ray tube is operated at the higher voltage to excite the ultraviolet phosphor, static information can be stored in the imagestorage panel and displayed by the action of an electroluminescent material thereby.

PATENTEUJAN! 1 1972 INVENTORS EUVAL s. BARREKETTE HERBERT B. BASKIN BENJAMIN KAZAN BY WWW FIG. 1

SWITCH CONTROL /-46 ATTORNEY This invention relates to display devices. More particularly, it relates to improved display devices capable of producing multipersistence displays.

The display devices in current use can be generally categorized as of two types. A first of these types is the display device which depends on regenerative displays, this type of device generally being a cathode-ray tube, lightbulb, etc., that requires signals to be continuously or repetitively fed to it in order to maintain a consistent and flicker free display. The second of these types is based upon those display technologies that have intrinsic storage capability in the display medium itself, an example of a device based upon such display technology being a storage cathode-ray tube.

In a publication by Benjamin Kazan and John S. Winslow in the Proceedings of the IEEE, Vol. 56, No. 3, on pages 285-294 and titled Image-Storage Panels Based on Field-Effect Control of Conductivity, there is disclosed a solid-state image panel which is capable of producing a stored luminescent image. This panel comprises a glass plate support whose surface is provided with a set of transparent conducting lines alternate ones of these lines being connected together to form an interdigitaling system with AC voltage being applied across the two sets of the line. The surface of the glass is coated with a layer of an electroluminescent phosphor which in turn is coated with a thin layer of zinc oxide powder. The zinc oxide layer serves as a control and storage purpose medi- In the operation of this panel, the exposed zinc oxide surface is first uniformly corona charged to a negative potential to reduce its conductivity and erase old information thereon. Thereafter, the panel is exposed to an optical image which discharges local areas to produce a stored charge pattern on the zinc oxide surface. In accordance with this stored charge pattern, a conductivity pattern is created in the zinc oxide layer which, in turn, controls the luminescent output of corresponding areas of the adjacent phosphor layer.

Since the above-described panel is capable of providing image storage, it is, therefore, advantageously employed for displaying static information. A display arrangement, particularly of the program-controlled type widely used in interactive graphics and capable of displaying both dynamic and static data would be extremely valuable in that it would result in much lower central processor overhead due to resulting lowering of requirements for display generation. This, in turn, would lead to the capability of providing more displays for a given size processor with a concomitant saving in communication with remote terminals.

Accordingly, it is an important object of this invention to provide a display arrangement capable of displaying information containing both dynamic and static components.

It is another object to provide a display arrangement in accordance with preceding object which is also capable of image-storing portions of the displayed information.

SUMMARY OF THE INVENTION Generally speaking and in accordance with the invention, there is provided a multipersistence display arrangement. The arrangement comprises a cathode-ray tube including means of generating an electron beam therein and a faceplate to support a screen therefor. n the inner surface of the faceplate, there is provided a layer of phosphor-emitting ultraviolet radiation. On the ultraviolet phosphor layer, there is disposed a phosphor layer-emitting visible light. A source for providing an anode voltage to the tube is included and means are also included for selectively applying a first and higher and a second and lower voltage between the anode and cathode of the tube. The application of the higher voltage causes the electron beam to penetrate the visible-emitting phosphor and excite the ultraviolet-emitting phosphor layer, while the application of the lower voltage causes the electron beam to excite the.

visible-emitting phosphor layer. An image-storage panel is provided for storing an ultraviolet image therein and optical means are included for imaging a radiation pattern as generated at the screen onto the panel which is stored and converted into a visible image if an ultraviolet image is generated by the cathode-ray tube.

The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention, as illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings,

FIG. 1 is a depiction and cross section of an image-storage panel as described hereinabove in the Kazan and Winslow publication; and

FIG. 2 is a diagram of an illustrative embodiment of a display arrangement constructed in accordance with the principles of the invention, and utilizing the panel shown in FIG. 1.

DESCRIPTION OF A PREFERRED EMBODIMENT In FIG. 1, there is shown an embodiment of the imagestorage panel 10 disclosed in the above-mentioned publication. The panel suitably comprises a plate 12 of glass or other light transparent insulating material. Applied to one surface of plate 12 are filmstrips of a light-transparent conductive coating 14 of tin oxide or other suitable conducting material, support plate 12 being coated with about 50 lines per inch of conductive film strip 14. A layer of an electroluminescent (EL) material 16 is provided on support plate 12 over conductive filmstrip l4, layer 16 being uniformly distributed over support plate 12 as a film about 1 to 2 mils-thick. A suitable material for layer 16 is one that emits light in the visible range of the electromagnetic spectrum, consisting, for example, of ZnS activated with copper and chlorine. A layer 18 of a photoconductive material which is sensitive to wavelengths shorter than that of visible light is uniformly disposed over electroluminescent layer 16, layer 18 comprising, for example, a photoconductive material such as zinc oxide.

As described in the above-mentioned paper, the alternate transparent conductive film strips 14 are connected to the leads 20 and 22, which are excited with AC voltage from source 24. In operation, current supplied by leads 20 and 22 flows through a conductive filmstrip 14 through electroluminescent layer 16, above the strip, across the photoconductive material layer 18 and back through to the adjacent phosphor and conductive strip 14.

Approximately 1 cm. from panel 10 is a set of fine wires 19 about 1 mil in diameter and which are about 1 cm. apart. Before imaging, panel 10 is erased by momentarily applying a negative voltage to wires 19 from a direct current source 26 by closing a switch 28, source 26 suitably being about 6 kv. Consequently, layer 18 becomes negatively charged by the corona emission from wires 19. Where layer 18 comprises zinc oxide, for example, as a result of the application of the DC corona voltage, the surface charge is in the form of negative oxygen ions. Following this charging process, portions of the zinc oxide surface are discharged or neutralized by free holes generated when the ZnO is locally exposed to ultraviolet radiation. In unexposed areas where the negative charges are retained, the conductivity of photoconductive layer 18 is low due to the depletion of mobile charges by field-effect action of the surface charges. The light output from the phosphor in these areas is thus low due to the limited current flow. However, in the regions where the photoconductor was irradiated, the conductivity of ZnO is relatively high. The local current between strips 14 is now increased, causing light to be emitted from the corresponding area of phosphor material. As has been mentioned, when the DC voltage from source 26 is applied to wires 19, the surface of photoconductive layer 18 is corona charged to erase panel 10. Now, when the panel is exposed to a transient image, a charge pattern in accordance with this image is created on the surface of photoconductive layer 18 which can be observed on the opposite side of the panel, i.e., through glass plate 12, as a luminescent image. Wires 19 are sufficiently thin so as to interrupt only a negligible portion of the light of the projected image.

As stated in the aforementioned Kazan, Winslow publication, panel may be fabricated by coating a surface of a Pyrex glass plate with the tin oxide transparent conductive layer. The tin oxide surface is then coated with a layer of a photoresist which is optically exposed through a suitable line mask to leave a pattern of photoresist lines after development. The exposed tin oxide areas between the photoresist line are then etched away. After this step, plate 12 is sprayed with an electroluminescent powder in an epoxy resin to provide layer 16 in a thickness of about 2 mils. This layer 16 is then coated with a photoconductive layer such as zinc oxide which is less than 1 mil thick, the photoconductive powder being in a suitable binder. Panels such as panel 10 have been fabricated in sizes up to 12x12 inches with conducting strips 14 on 20-mil centers and 10 mils wide.

Reference is now made to F IG. 2 wherein there is shown an illustrative embodiment of a multipersistence display arrangement constructed in accordance with the invention. In this embodiment, there is provided a cathode-ray tube which comprises a glass envelope 3], an electron gun 32 with a cathode 31 for generating an electron writing beam, and

beam-deflecting plates.

Coated on the inner surface of the faceplate of tube 30 is a layer 34 of an ultraviolet-emitting (UV) phosphor such as, for example, P16. On UV phosphor layer 34, there'is disposed a layer of visible phosphor 36 such as type P1 or P31. This phosphor is in turn coated with a thin aluminum film 27 which is transparent to the cathode-ray beam. The acceleration voltage for tube 30 is provided from the DC source 38 which is shown as being developed across a resistance 40. The anode voltage for tube 30 can be taken from two points in source 38, across the bleeder resistor 40. The position of a switch 41 determines whether the full voltage or lesser voltage from source 38 is applied between the cathode and screen of the tube. Switch 41, although depicted as a mechanical switch for convenience of illustration, is actually an electronic switch, such switch being activated in response to the action of a stage 44 legended switch logic. Switch logic stage 44 can suitably comprise digital logic. Such logic is well known in the art and no further description thereof is deemed necessary. A control stage 46 is included in FIG. 2 to illustrate how the switch logic can be controlled by an independent control source. For example, control stage 46 can be the control system for an interactive graphics system and could be computer programmed to control a display device, an interfacing channel and the like.

In the operation of the arrangement shown in FIG. 2, upon the closing of switch 41 whereby the greater of the two voltages is applied from source 38 as the anode voltage to tube 30, the beam generated from gun 32 is caused to penetrate to the phosphor layer further from the gun, i.e., UV phosphor layer 34. Similarly, upon the closing of switch 41 whereby the lesser of the two voltages from source 38 is applied as the anode voltage to tube 30, the electron beam is permitted to excite only the visible-emitting phosphor layer 36. The resultant radiation pattern appearing on the screen of the tube 30 is projected onto panel 10 through an optical imaging system schematically shown as lens 48.

It is seen that when the electron beam is caused to scan the nearer and visible-emitting phosphor layer 38, the visible image appears on the screen of tube 30 which is seen through the opposite side 12 of panel 10 as depicted by the arrows pointed away therefrom. This image does not excite the panel, but is seen because of the translucent nature of the panel layers. When the electron beam is caused to scan the further and UV-emitting phosphor layer 34, the ultraviolet image generated is projected onto panel 10 through optical system 48, causing the image to be stored on the panel through the action of its field-effect photoconductive layer. This image is rendered visible by the electroluminescent layer of panel 10 and can also be viewed through the transparent support plate 12. Thus, with this invention, nonstored dynamic information can be displayed using the lower accelerating voltage to excite phosphor layer 36, and a stored image can be created by using the higher accelerating voltage to excite UV phosphor layer Although not discussed above, in place of the cathode-ray tube 30 other types of multicolor cathode-ray tubes can be used for generating an output image which can be electronically switched to emit either in the ultraviolet portion of the spectrum or in the visible. For example, a shadow-mask type of color cathode-ray tube can be used (A three-Gun Shadow- Mask Color Kinescope," by H. B. Law, Proc. of lRE, Vol. 39, Oct. ll,pp. 1186-1194).

In this case, the screen may consist of two sets of phosphor dots, one set emitting ultraviolet light and the other set emitting visible light such as green. By employing two electron guns suitably positioned, an ultraviolet or visible image may be generated depending on whether the input signals are fed to one gun or the other.

What is claimed is:

1. A multipersistence display arrangement comprising:

a cathode-ray tube including means for generating an electron beam therein and a faceplate to constitute a screen therefor;

a layer of an ultraviolet-emitting phosphor on the inner surface of said faceplate;

a layer of visible-emitting phosphor disposed on said ultraviolet phosphor layer;

means for applying a first and higher voltage as an anode voltage to said tube to cause said electron beam to excite said ultraviolet-emitting phosphor-layer to produce an ultraviolet image therefrom;

means for applying a second and lower voltage an as anode voltage to cause said electron beam to excite said visibleemitting phosphor layer to produce a visible image therefrom;

an image-storage panel for storing said ultraviolet image therein; and

optical means for imaging an image from said screen onto said panel to store said utraviolet image.

2. A multipersistence display arrangement as defined in claim 1 wherein said image-storage panel comprises:

a support member of a material which is transparent to light;

a layer of visible electroluminescent material supported on one side of said support member;

a layer of a photoconductive material on said visible electroluminescent material layer, said photoconductive material being chosen to be one which is sensitive to light wavelengths less than that of visible light;

a layer of light transparent conductive material interposed between said support member and said visible electroluminescent material which upon the application of a voltage thereto establishes a potential across said photoconductive material layer and said visible electroluminescent material layer to render an image stored in said photoconductive layer visible by the consequent luminescing of said visible electroluminescent material, said image being viewable through said transparent panel support member, said image from said cathode-ray tube being imaged onto said photoconductive material layer.

3. A multipersistence display arrangement as defined in claim 2 wherein said photoconductive material is zinc oxide.

4. A multipersistence display arrangement as defined in claim 3 wherein there are further included means associated with said photoconductive material layer for charging said layer to erase any image stored therein and to prepare it for receiving a new ultraviolet light image.

5. A multipersistence display arrangement comprising:

a cathode-ray tube including means for generating an electron beam therein and a faceplate to constitute a screen therefor;

a layer of an ultraviolet-emitting phosphor on the inner surface of said faceplate;

a layer of a visible-emitting phosphor disposed on said ultraviolet phosphor layer;

means for selectively applying a first and higher voltage as an anode voltage to said tube to cause said electron beam to excite said ultraviolet-emitting phosphor layer to produce an ultraviolet image therefrom. and a second and lower voltage as an anode voltage to said tube to cause said electron beam to scan said visible-emitting phosphor layer to produce a visible image therefrom;

an image-storage panel for storing said ultravioletimage therein, said panel including a layer of photoconductive material which is sensitive to light wavelengths which are shorter than that of visible light;

optical means for imaging an image from said screen onto said panel to store said ultraviolet image in said photoconductive layer.

6. A multipersistence display arrangement as defined in claim 5 wherein said means for selectively applying said higher and lower voltages comprises switching means and wherein said arrangement is adapted to be controlled by control means, said control means determining the selection of said voltages through said switching means. 

1. A multipersistence display arrangement comprising: a cathode-ray tube including means for generating an electron beam therein and a faceplate to constitute a screen therefor; a layer of an ultraviolet-emitting phosphor on the inner surface of said faceplate; a layer of visible-emitting phosphor disposed on said ultraviolet phosphor layer; means for applying a first and higher voltage as an anode voltage to said tube to cause said electron beam to excite said ultraviolet-emitting phosphor layer to produce an ultraviolet image therefrom; means for applying a second and lower voltage an as anode voltage to cause said electron beam to excite said visibleemitting phosphor layer to produce a visible image therefrom; an image-storage panel for storing said ultraviolet image therein; and optical means for imaging an image from said screen onto said panel to store said utraviolet image.
 2. A multipersistence display arrangement as defined in claim 1 wherein said image-storage panel comprises: a support member of a material which is transparent to light; a layer of visible electroluminescent material supported on one side of said support member; a layer of a photoconductive material on said visible electroluminescent material layer, said photoconductive material being chosen to be one which is sensitive to light wavelengths less than that of visible light; a layer of light transparent conductive material interposed between said support member and said visible electroluminescent material which upon the application of a voltage thereto establishes a potential across said photoconductive material layer and said visible electroluminescent material layer to render an image stored in said photoconductive layer visible by the consequent luminescing of said visible electroluminescent material, said image being viewable through said transparent panel support member, said image from said cathode-ray tube being imaged onto said photoconductive material layer.
 3. A multipersistence display arrangement as defined in claim 2 wherein said photoconductive material is zinc oxide.
 4. A multipersistence display arrangement as defined in claim 3 wherein there are further included means associated with said photoconductive material layer for charging said layer to erase any image stored therein and to prepare it for receiving a new ultraviolet light image.
 5. A multipersistence display arrangement comprising: a cathode-ray tube including means for generating an electron beam therein and a faceplate to constitute a screen therefor; a layer of an ultraviolet-emitting phosphor on the inner surface of said faceplate; a layer of a visible-emitting phosphor disposed on said ultraviolet phosphor layer; means for selectively applying a first and higher voltage as an anode voltage to said tube to cause said electron beam to excite said ultraviolet-emitting phosphor layer to produce an ultraviolet image therefrom, and a second and lower voltage as an anode voltage to said tube to cause said electron beam to scan said visible-emitting phosphor layer to produce a visible image therefrom; an image-storage panel for storing said ultraviolet image therein, said panel including a layer of photoconductive material which is sensitive to light wavelengths which are shorter than that of visible light; optical means for imaging an image from said screen onto said panel to store said ultraviolet image in said photoconductive layer.
 6. A multipersistence display arrangement as defined in claim 5 wherein said means for selectively applying said higher and lower voltages comprises switching means and wherein said arrangement is adapted to be controlled by control means, said control means determining the selection of said voltages through said switching means. 